1. Field of the Invention
The present invention relates to a process for the preparation of pyrazolone derivatives that are useful as intermediate starting materials for synthesizing agricultural chemicals, medicine and chemical compounds.
2. Prior Art
The following methods have heretofore been known for obtaining a pyrazolone or 1-substituted-3-pyrazolones.
(1) A method of reacting an .alpha.- or an .alpha., .beta.-ester-substituted acetylene with a hydrazine compound or a hydrazone compound (CA 75:110227, CA 81:13426).
(2) A method of reacting a .beta.-keto-acid ester with a hydrazine compound (CA 105:42788, Yakugakushi 60, 45, 1940).
(3) A method of reacting a .beta.-chlorolactic acid ester with a hydrazine (Chem. Ber 27 407, 1894).
(4) A method of treating a 3-(N-phenylhydrazino) propionitrile with an alcoholic alkali (Boll Sci. Fac. Chim. Ind. Bolongna 11 78, 1953).
(5) A method of subjecting a corresponding pyrazolidone derivative to a treatment such as oxidation (Chem. Ber 29 519, 1896).
(6) A method of decarboxylating a carboxylate of a corresponding pyrazolone (Chem. Ber 40, 1021, 1907).
According to the above-mentioned methods (1) to (4), however, the starting materials are not usually easily available or are expensive. According to the above-mentioned methods (5) and (6), a step of cyclization reaction is necessary for synthesizing starting materials resulting in a substantial increase in the number of the steps.
As described above, the prior art for synthesizing pyrazolone derivatives is quite unsatisfactory as an industrial process since the starting materials are not easily available or are expensive, or the operations are cumbersome.